Glenn McGillivray is the managing director of the Institute for Catastrophic Loss Reduction.

A large wildfire in Alberta in May? This must be the work of climate change, right?

Truth be told, early May is a prime time for wildfires in Alberta, even in the province’s north, and the past reflects this well. The 2016 wildfire in Fort McMurray and the 2011 one in Slave Lake both occurred in May, as did the huge Chisholm fire, which burned more than 120,000 hectares southeast of Slave Lake in spring 2001.

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Much of Western Canada actually experiences two distinct wildfire seasons. There’s the late summer/early fall season that most people are familiar with, when forests can be tinder-dry after prolonged periods of high heat and little or no precipitation. But areas close to or in the boreal forest, like northern Alberta, are currently in the midst of the lesser-known wildfire season, the period after the snow stops but before the forest greens up and sequesters the moisture that makes these large, intense fires that spread treetop to treetop less likely.

Really, all you need for a large, aggressive wildfire is low relative humidity, the right fuel and a source of ignition. High temperatures and brisk winds will add to the risk, but aren’t obligatory ingredients. Indeed, while the temperature was relatively low in the immediate run-up to the Slave Lake wildfire – there was still patchy snow in the bush about a week before – relative humidity was low and winds were high. Add an ignition source, and you’re off to the races.

Conversely, the fire in Fort McMurray came after a mild winter with low snow pack. The drought index around the time of the fire was quite high, as was the temperature. Add high winds and an ignition source and voila: you get Canada’s costliest insured disaster.

But does any of this mean that climate change is not now, nor will be, a factor in such fires?

The answer, of course, is no. But it’s complex.

The reality is climate is a complicated stew made up of all kinds of different ingredients. Human-made climate change is just one of them, a spice that contributes to the overall flavour of the stew, but is difficult to single out when you have a little taste. You know it’s there, and you know it plays a role in flavouring the stew, but it is difficult to say exactly just how much.

Increasingly, though, science has gotten to the point where we can now look at a particular hazard event and determine what specific role climate change played in the way that event unfolded. Known as attribution science, we can clearly state that climate change contributed to a particular event and put a number on that contribution.

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We can now bring data to bear against a sophomoric argument favoured by climate-change deniers – that if we could have natural disasters in the past when current climate change wasn’t yet on the radar, then similar events today can’t be associated with a warming climate. That seriously (and perhaps intentionally) misses the point of climate change.

Climate change is a force multiplier: It doesn’t directly produce severe weather, but it does nurture and amplify it. It takes something that likely would have happened anyway and makes it worse. It also loads the dice, making severe-loss events more likely to happen.

In the case of wildfire, climate change can mean a fire season that begins earlier than before. It can mean bigger, hotter, faster-moving fires. It can mean more lightning, which is the cause of roughly half of all wildfires in Canada. It can also mean a season that can extend later.

We have already observed a marked change in Canada’s fire regime, as the area burned in the country has doubled since just the early 1970s – and that number is projected to double again by the end of the century.

And just two weeks ago, at the end of the day on May 11, scientists measured more than 415 parts per million of carbon dioxide in the atmosphere – the highest such day-end measurement in human history. To put this very worrisome metric into context, the last time Earth had more than 415 ppm of CO2 in its atmosphere, homo sapiens did not yet exist.

We are the new kids on the block. Fire has been a critical part of our ecosystem since long before we came around. So it is not so much that fire regularly seeks out our communities to try to destroy them – it’s that humans have put communities in its way.

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Somehow, we have to work out this standoff – to learn to live with fire, as it were. The alternative will be that we will forever have to be on guard.

And that’s no way to live.

Editor’s note: An earlier version of this article stated that the Fort McMurray fire was Canada’s costliest natural disaster; however, it was Canada’s costliest insured disaster. This version has been updated.

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